Highly Effective Proton-Conductive Matrix-Mixed Membrane Based on a −SO3H‑Functionalized Polyphosphazene

• Published in: Langmuir 2022-08, Vol.38 (34), p.10503-10511
• Main Authors: Afzal, Jamal, Fu, Yaomei, Luan, Tian-Xiang, Su, Zhongmin, Li, Pei-Zhou
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.2c01273

A polyphosphazene with in-built −SO3H moieties (PP-PhSO 3 H) was facilely synthesized by the polymeric combination of hexachlorocyclotriphosphazene (HCCP) and sulfonate p-phenylenediamine. Characterization reveals that it is a highly stable amorphous polymer. Proton conductivity investigations showed that the synthesized PP-PhSO 3 H exhibits a proton conductivity of up to 6.64 × 10–2 S cm–1 at 353 K and 98% relative humidity (RH). This value is almost 2 orders of magnitude higher than the corresponding value for its −SO3H-free analogue, PP-Ph, which is 1.72 × 10–4 S cm–1 when measured under the same condition. Consequently, matrix-mixed membranes (labeled PP-PhSO 3 H-PAN) were further prepared by mixing PP-PhSO 3 H with polyacrylonitrile (PAN) in different ratios to test its potential application in the proton-exchange membrane (PEM) fuel cell. The analysis results indicate that when the weight ratio of PP-PhSO 3 H/PAN is 3:1 [named PP-PhSO 3 H-PAN (3:1)], its proton conductivity can reach up to 5.05 × 10–2 S cm–1 at 353 K and 98% RH, which is even comparable with those of proton-conductive electrolytes currently used in PEM fuel cells. Furthermore, the continuous test demonstrates that the PP-PhSO 3 H-PAN (3:1) has long-life reusability. This research reveals that by using phosphazene and sulfonated multiple-amine modules as precursors, organic polymers with excellent proton conductivity for the assembly of matrix-mixed membranes in PEM fuel cells can be easily synthesized by a simple polymeric process.